Extended X-ray absorption fine structure studies of magnetic nanoparticles

Abstract

We have synthesized nickel by means of pulsed laser ablation. A nickel disc was used for ablation with the focused output of fundamental harmonic from Nd: YAG laser. X-ray diffraction result shows that the synthesized nanoparticles are of pure metallic nickel with a face-centred cubic structure and the average particle size is 35 nm. The extended X-ray absorption fine structure (EXAFS) studies of pure nickel foil and the synthesized nanoparticles show similar structures. The position of the main peak is same in these nanoparticles with reference to the nickel foil. The only difference was observed in the reduction of the amplitude. The nearestneighbour distance is similar as for pure nickel foil. The Debye-Waller factor is also similar. There is no trace of oxide and hydroxide in the EXAFS data, suggesting that the synthesized nanoparticles contain only nickel metal. IntroductionNanoscience involves a study of materials where at least one of the dimensions is in the 1-100 nm range. Properties of such materials are strongly dependant on their size and shape. Nanomaterials are produced by physical methods such as laser ablation, arc-discharge and evaporation. Among these methods pulsed laser ablation in liquid (PLAL) media is an emerging technique in material science for fabricating metal and metal-oxide nanoparticles.Laser ablation of a metal in a liquid medium is of particular interest because of its strong non-equilibrium process. The nanostructure formation by laser ablation liquid is mainly due to the combination of ultra-fast quenching of hot plasma and its interaction with surrounding media. The sodium dodecyle sulfate (SDS) can be attributed to the capping effect on the nanoparticles. SDS solution adsorbs on the Ni nanoparticles surface and this capping will prevent not only oxidation of the particles but also the coalescence among particles due to repulsive interaction, leading to stable colloidal solution and small-sized particles.